1. Field of the Invention
The present invention relates to a liquid ejection head and a method of manufacturing a liquid ejection head, and more particularly, to a liquid ejection head and a method of manufacturing a liquid ejection head in which pressure chambers are deformed by means of piezoelectric elements disposed on a diaphragm, and liquid is ejected from ejection ports connected to the pressure chambers.
2. Description of the Related Art
An inkjet recording apparatus is known as one apparatus for recording text characters and images onto a recording medium, such as paper. An inkjet recording apparatus forms images by means of ink dots, by causing ink to be ejected from a recording head comprising nozzles for ejecting ink, in accordance with an image signal, thereby depositing ink droplets onto a print medium, while moving the recording medium relatively with respect to the print head. Typical ink ejection methods are known in which ink is ejected from a nozzle by a bubble generated inside a pressure chamber, or ink is ejected from a nozzle by means of a volume change in a pressure chamber.
In a method which ejects ink from a nozzle by means of a volume change in a pressure chamber, the volume of the pressure chamber is generally changed by using a piezoelectric element. In this case, the piezoelectric element is disposed on a diaphragm which constitutes one portion of the pressure chamber, and a drive voltage is applied to the piezoelectric element through a flexible printed circuit (FPC). However, if the flexible printed circuit and the piezoelectric element are disposed in contact with each other, then there is a problem in that the deformation of the piezoelectric element is restricted. Furthermore, if ink reaches the piezoelectric element, then there is a risk of the piezoelectric element being shorted by this ink.
Japanese Patent Application Publication No. 6-286126 discloses that an adhesive layer is formed so as to surround the peripheries of piezoelectric elements, and the piezoelectric elements are sealed hermetically inside spaces by bonding a flexible printed circuit by means of this adhesive layer, and furthermore, projections are formed so as to surround the peripheries of piezoelectric elements and the piezoelectric elements are sealed hermetically inside spaces by fixing a flexible printed circuit to the projections, by means of an adhesive.
Japanese Patent Application Publication No. 2002-46281 discloses that a bonding substrate formed integrally with an integrated circuit is bonded through a sealing member onto a flow channel substrate on which piezoelectric elements are provided, and by connecting the piezoelectric elements with the integrated circuit through lead electrodes, the piezoelectric elements are hermetically sealed inside the spaces demarcated by the bonding substrate and the sealing member.
However, in Japanese Patent Application Publication No. 6-286126, since the flexible printed circuit is actually supported by the adhesive layer, the thickness of the adhesive layer is reduced by the bonding pressure, and the flexible printed circuit makes contact with the piezoelectric elements, thereby restricting the piezoelectric elements and thus preventing stable ejection. Furthermore, since the movable portion and the electrical connection portion of the piezoelectric element are not demarcated, then it is necessary to provide a conductive material locally on the electrode of the piezoelectric element, thus giving rise to problems of increased manufacturing work and the occurrence of variations.
Moreover, in Japanese Patent Application Publication No. 2002-46281, the flow channel substrate and the bonding substrate must be made of monocrystalline silicon, and hence there is no freedom in the choice of material. Furthermore, if the sealing member is made of adhesive only, then in order to seal off the piezoelectric elements individually, the adhesive must be applied in a very fine pattern, and therefore, the process becomes highly complex. On the other hand, if the sealing member is made of a hard material, such as glass or silicon, then it is not possible to demarcate completely the movable portion and the electrical connection portion of the piezoelectric element, and therefore a conductive material must be provided locally on the electrical connection portion of the piezoelectric element, thus giving rise to problems of increased manufacturing work and the occurrence of variations.